Abstract
Transition-metal-catalyzed C‒C bond formation reaction by uniting readily available π-components is an attractive strategy to synthesis biologically important compounds in a single operation with high atom-efficacy. Particularly, C H bond activation reactions are experienced method to synthesis of natural products and biologically important compounds in a highly regioselective manner. The C H functionalization of aryl aldehydes with amines and alkynes to afford highly substituted isoquinolines. On the other hand multiple C H activations of N-hyroxybenzamidines with alkynes afforded highly substituted hetroaromatic compounds in one-pot manner. For better understanding, I divided this thesis into four chapters. The first three chapters describe about rhodium-catalyzed inter and intramolecular C-H activation/annulation of aldehydes with amines and alkynes or (amino-alkynes). The final chapter describe about the multiple C H activations of N-hyroxybenzamidines or (aryl nitrile and amines) with alkynes using rhodium(III) as the catalyst. Chapter 1 describes a new method for the synthesis of isoquinolinium salts from the oxidative coupling/annulation of alkynes with aldehydes and amines via Rh(III) catalysis. The proposed mechanism is strongly supported by the isolation of a five-membered rhodacycle and an intermediate organic compound. This protocol successfully applied to the total synthesis of Oxychelerythrine with 66% overall yield. Chapter 2 deals with the synthesis of quaternary protoberberine alkaloids (QPA) from aldehydes and aminoalkynes with Rh(III)-salt complex. The reaction can be applied to a straight forward synthesis of 13-substituted protoberberine natural products. Chapter 3 illustrates a rhodium-catalyzed synthesis of N-heterocycles from aldehydes, amines and alkynes by C-H activation method. This is the first example of an imine-directed synthesis of highly substituted isoquinolones in one-pot. Chapter 4 is about the synthesis of polyhetreoaromatics from N-benzamidines and alkynes by multiple rhodium-catalyzed C H activation and annulation steps. A possible mechanism is proposed involving multi-step chelation-assisted ortho-C–H activation, alkyne insertion and reductive elimination